The present disclosure relates to a dot sight device for use in a small arm such as a handgun, a pistol, or a rifle, and more particularly, to a dot sight device for use in a small arm which is capable of aligning a principal ray among light rays from a dot reticle image of a dot sight device with a gun barrel of a small arm without causing a change in a relative position between a mask and a reflective mirror.
Small arms such as handguns, pistols, or rifles have a short distance of fire, and in order to increase an accuracy rate, a gun barrel needs to be aligned with an optical axis (an axis through which a principal ray among light rays from a dot reticle image passes) of a dot sight device. Here, a principal ray refers to a representative ray passing through the center of an effective portion of a reflective mirror of a dot sight device. For this reason, dot sight devices for small arms have increasingly employed a mechanism capable of aligning a gun barrel with an optical axis of a dot sight device.
An optical device with a mechanism that aligns a gun barrel of a handgun with an optical axis of an optical device by adjusting the position of a light emitting diode (LED) that provides a dot reticle is disclosed in U.S. Pat. No. 6,327,806. FIG. 1 is an exploded perspective view illustrating a dot sight device for used in a small arm with a mechanism disclosed in U.S. Pat. No. 6,327,806. Referring to FIG. 1, an elevation adjustment screw 17 used to move an LED with a reticle or a mask (hereinafter, “mask”) fixed to the front thereof from a focal position of a reflective mirror 1 in the horizontal direction, and an azimuth adjustment screw 18 used to move the LED from the focal position of the reflective mirror 1 in the vertical direction are provided. A gun barrel is aligned with a dot reticle image that is reflected from the reflective mirror and then directed toward an observer by turning the elevation adjustment screw 17 or the azimuth adjustment screw 18 according to need.
However, in the mechanism disclosed in U.S. Pat. No. 6,327,806, since the relative position of the LED is adjusted in a state in which the reflective mirror 1 is fixed, the dot reticle provided from the LED is likely to deviate from the focal point of the reflective mirror 1 in the process of adjustment. Thus, there is a problem in that parallax between light rays which are reflected from the reflective mirror and then incident to the observer's eye(s) and a target viewed through the reflective mirror significantly occurs in the edge portion of the reflective mirror. In other words, since the relative position of the LED relative to the reflective mirror, that is, the relative position of the mask relative to the reflective mirror is changed, parallax of the dot sight device changes.
More specifically, when a doublet shown in Table 1 is used as a reflective mirror and a second surface of the double functions to reflect a dot reticle, a directional finite ray aberration of light rays, which are reflected from the reflective mirror and then incident on the observer's eye(s) in the state in which the dot reticle is positioned on the focal point of the reflective mirror, is about 0.14 milliradians as illustrated in FIG. 2A. In FIGS. 2A and 2B, an x axis represents the effective diameter of the reflective mirror, and a y axis represents a directional finite ray aberration.
TABLE 1Focal distance (f)−27.2893 mmThickness (t1) of first lenst1 = 2.00 mmCurvature radius (R1) ofR1 = −28.484 mmfirst surfaceThickness (t2) of secondt2 = 2.50 mmlensCurvature radius (R2) ofR2 = −43.116 mmsecond surfaceCurvature radius (R3) ofR3 = −30.014 mmthird surfaceglassBK7Effective diameterVertical size: 12.5 mmHorizontal size: 25.0 mm
In the dot sight device employing the reflective mirror shown in Table 1, when the position of the dot mask is changed from the state in which the dot reticle is positioned on the focal point of the reflective mirror for zeroing, for example, when 0.5 mm is changed downward, and 0.5 mm is changed rightward, the dot reticle deviates from the focal point of the reflective mirror. In this case, a directional finite ray aberration of light rays, which are reflected from the reflective mirror and then incident on the observer's eye(s), is about 1.21 milliradians as illustrated in FIG. 2B, and an parallax error of reflected light rays in the edge portion of the reflective mirror increases to be about 860 times as large as that of FIG. 2A.